SV40 T antigen is involved in malignant cell transformation and viral replication. According to biological and biochemical evidence this viral gene product accomplishes its potent effects via its interactions with cellular and viral DNA. The properties of T antigen will be examined by analysis of its post-translational modifications including phosphorylation and glycosylation. The relationship of these processes to the specific DNA affinities and oligomerization of T antigen in permissive and transformed cells will be investigated. We will attempt to isolate cellular DNA sequences in transformed cells for which active T antigen has specific affinity. Various aspects of T antigen expression will be analyzed. mRNA known to code for the T antigens will be used to study processes such as splicing and other post transcriptional modifications. We will investigate differences in T antigen mRNA isolated from lytically infected and transformed cells in terms of these modifications and also with regard to intracellular localization and cytoskeleton. Host regulation of T antigen mRNA expression will also be studied in revertants isolated from SV40 transformants.